Imidazolinyl benzamides as plant growth regulants

ABSTRACT

This invention relates to a method for regulating the growth of crop plants by applying to the foliage, roots, stems, seeds or to soil in which the crop plants are grown, an effective plant growth regulating amount of an imidazolinyl benzamide having the structure: ##STR1## wherein R 1  is alkyl C 1  -C 4  ; R 2  is alkyl C 1  -C 6 , cycloalkyl C 3  -C 6 , alkenyl C 2  -C 4 , phenyl, halophenyl or benzyl; and when R 1  and R 2  are taken together with the carbon to which they are attached they may form cycloalkyl C 3  -C 6  optionally substituted with methyl; R 3  and R 4  each individually represent hydrogen, alkyl C 1  -C 4 , alkenyl C 3  -C 5 , alkynyl C 3  -C 5 , or benzyl; and when R 1  and R 2  represent different substituents, the optical isomers thereof.

DETAILED DESCRIPTION OF THE INVENTION

This invention relates to a method for regulating the growth of graminaceous crops and bean-producing legumes, by applying to the foliage, roots, stems, seeds, or to soil in which said crop plants are grown, an effective plant growth regulating amount of an imidazolinyl benzamide having the structure: ##STR2## wherein R₁ is alkyl C₁ -C₄ ; R₂ is alkyl C₁ -C₆, cycloalkyl C₃ -C₆, alkenyl C₂ -C₄, phenyl, halophenyl or benzyl; and when R₁ and R₂ are taken together with the carbon to which they are attached they may form cycloalkyl C₃ -C₆ optionally substituted with methyl; R₃ and R₄ each individually represent hydrogen, alkyl C₁ -C₄, alkenyl C₃ -C₅, alkynyl C₃ -C₅, or benzyl; and when R₁ and R₂ represent different substituents, the optical isomers thereof.

The compounds useful herein are disclosed and claimed in coassigned U.S. Ser. No. 822,459, filed Aug. 8, 1977, in the name of Marinus Los now U.S. Pat. No. 4,122,275.

The invention also relates to a method for inhibiting axillary growth on topped tobacco plants and woody plant species such as coffee trees by applying a bud growth inhibiting amount of a formula (I) imidazolinyl benzamide to the foliage and/or to the soil at the base of the stems of topped tobacco plants or to the trunks of said coffee trees.

Preferred compounds for the above-described utilities have the structure of formula I above, wherein R₁ is methyl; R₂ is alkyl C₁ -C₃ (preferably isopropyl), or when R₁ and R₂ are taken together with the carbon to which they are attached they may represent cyclohexyl; R₃ and R₄ each individually represent hydrogen, alkyl C₁ -C₃ ; and when R₁ and R₂ are different, the optical isomers thereof.

In accordance with the present invention, the plant growth regulating effects of formula I imidazolinyl benzamides applied to graminaceous crops, such as barley, oats, wheat, rice and corn, and to bean-producing legumes, such as snapbeans, lima beans, soybean and green beans, are generally characterized by a reduction in the relative stem growth of such crops. The treated crop plants are generally shorter and stockier than untreated plants and are less susceptible to lodging when subjected to atmospheric disturbances, such as wind and rain.

In practice, it is generally found that application of about 0.03 kg to 3.36 kg per hectare, and preferably 0.03 kg to 1.12 kg per hectare, of the active formula I imidazolinyl benzamide to the foliage, stems, roots, seeds, or to soil in which the crops are grown, provides the desirable reduction of relative stem growth (dwarfing) of graminaceous crops and bean-producing legumes.

In tobacco farming, maturation of the crop for harvesting is nitrated by removal of the apical flower growth of the tobacco plant in a process known as "topping." This process facilitates the development of large leaves which form the commercial crop. Their development, however, is offset by the enhanced development of laterial (axillary) buds. The laterial growth (called "sucker growth") again reduces the nutrient supply available for large leaf development. Thus, it is essential to control sucker growth on the tobacco plants if optimal production of marketable leaves is to be achieved.

It has also been found that about 4 mg to 150 mg of the formula I imidazolinyl benzamide applied to the foliage and stems or to soil at the base of the stems of topped tobacco plants will inhibit axillary growth on said plants. Similarly, application of the formula I imidazolinyl benzamide to the trunks of coffee trees, at the rate of about 500 mg to 3000 mg per tree, inhibits bud growth and sucker development on said coffee trees.

For use in accordance with the present invention, the formula I imidazolinyl benzamides are generally formulated as wettable powders, flowable liquids, emulsifiable concentrates or granular formulations. The wettable powders, flowable liquids and emulsifiable concentrates are then dispersed in water or an inexpensive organic solvent for application as liquid sprays. These solutions or dispersions may, of course, also be applied as brush applications, as is frequently done in the treatment of the trunks of coffee trees.

Wettable powders can be prepared by grinding together about 20% to 45% by weight of a finely divided carrier such as attapulgite, bentonite, kaolin, diatomaceous earth, or the like, 45% to 80% by weight of the imidazolinyl benzamide, 2% to 5% by weight of a dispersing agent such as the sodium salt of condensed naphthalene sulfonic acids, sodium lignosulfonate, or the like, and 2% to 5% by weight of a surfactant such as sodium N-methyl-N-oleoyl taurate, alkyl phenoxy polyoxyethylene ethanol, or the like.

A typical flowable liquid can be prepared by admixing about 40% by weight of the formula I benzamide with about 2% by weight of gelling clay, 1% by weight of polyethylene glycol, 3% by weight of the sodium salt of condensed naphthalene sulfonic acids and 54% by weight of water.

A typical granular formulation can be prepared by dissolving or dispersing the active ingredient in solvent and applying the solution or dispersion to a sorptive or non-sorptive carrier in sufficient amount to provide 5% to 15% by weight of toxicant on the granular carrier; and a typical emulsifiable concentrate, can be prepared by dissolving about 25% by weight of the formula I imidazolinyl benzamide in 50% by weight of cyclohexanone, 15% by weight of a heavy aromatic solvent such as HiSol, Panasol AN-2, Esso HAN, or the like. While the imidazolinyl benzamides of this invention are illustrated by the structure identified as formula (I) above, it should be understood that these compounds may be tautomeric. As such, they could have the structure: ##STR3## wherein R₁, R₂, R₃ and R₄ are as described. Both tautomeric forms are, of course, intended to be included as compounds of the invention when reference is made throughout the specification and claims to the formula I structure.

In accordance with the invention, imidazolinyl benzamides having the structure: ##STR4## wherein R₁, R₂, R₃ and R₄ are as described above, can be prepared by reacting an imidazoisoindoledione having the structure: ##STR5## where R₁ and R₂ are as described above, with an amine represented by the formula: R₄ R₃ NH (III) where R₃ and R₄ are as described above.

The mole ratio of amine (III) to imidazoisoindoledione (II) should be in the range of 1:1 to 10:1, and preferably 2:1 to 5:1. The reaction is preferably conducted in a non-protic solvent such as tetrahydrofuran, dioxane, toluene, xylene, benzene, or the like, at a temperature between 50° C. and 100° C.

The reaction may be graphically illustrated as follows: ##STR6## wherein R₁, R₂, R₃ and R₄ are as described above.

It should also be understood that when R₁ and R₂ represent different substituents, the carbon to which R₁ and R₂ are attached is an asymmetric center and the products (as well as their intermediates) exist in d- and l- forms as well as dl- forms. Further, when the imidazoisoindoledione (II) is optically active and either the d- or l- isomer is reacted with the formula (III) amine, R₄ R₃ NH, the corresponding d- or l-imidazolinyl benzamide (I) is formed.

The intermediate imidazoisoindoledione (II), which are essential to the preparation of the formula (I) imidazolinyl benzamides of the present invention, are described, with a method for their preparation in U.S. Pat. No. 4,017,510, issued Apr. 12, 1977, Ser. No. 631,357, filed Nov. 12, 1975, and incorporated herein by reference thereto.

The invention in the present application is further demonstrated by the examples set forth below.

EXAMPLE 1 Preparation of o-(5-Isopropyl-5-methyl-4-oxo-2-imidazolin-2-yl)-N,N-dimethylbenzamide.

To a cold solution of 180 g of 3-isopropyl-3-methyl-5H-imidazo[2,1-a] isoindole-2-(3H), 5-dione in 300 ml of dry tetrahydrofuran in a pressure bottle is added 68 g of dimethylamine. The bottle is sealed and the mixture heated to 50° C. with stirring for 16 hours. The mixture is cooled, and the contents of the bottle transferred to a flask. The solvent is then removed in vacuo. The crystalline residue is then suspended in ether, filtered, washed with ether, and air-dried to give 195 g of o-(5-isopropyl-5-methyl-4-oxo-2-imidazolin-2-yl)-N,N-dimethylbenzamide, melting point 144°-146° C. This product is recrystallized from acetonitrile to give an analytically pure product, melting point 147°-150° C.

EXAMPLE 2 Preparation of Formula I Imidazolinyl Benzamides.

Using essentially the same procedure as that described in Example 1, but substituting the appropriate imidazo-[2,1-a]isoindole-2(3H), 5-dione and the appropriate amine for dimethylamine, yields the compounds set forth below.

    ______________________________________                                          ##STR7##                                                                                                          Melting                                                                        Point                                      R.sub.1                                                                               R.sub.2   R.sub.3  R.sub.4   °C.                                 ______________________________________                                         (CH.sub.2).sub.5                                                                            H        H           211-212                                      CH.sub.3                                                                              CH(CH.sub.3).sub.2                                                                       H        H         174-175                                    CH.sub.3                                                                              CH(CH.sub.3).sub.2                                                                       H        CH.sub.3  203-204                                    (CH.sub.2).sub.5                                                                            CH.sub.3 CH.sub.3    189-190.5                                    (CH.sub.2).sub.5                                                                            H        CH.sub.3    259-261                                      CH.sub.3                                                                              CH(CH.sub.3).sub.2                                                                       H        CH.sub.2 CCH                                                                             202-205                                    ______________________________________                                    

EXAMPLE 3 Plant Growth Regulating Effect of Test Compounds Applied to the Foliage of Plants

To evaluate test compounds as plant growth regulating agents effective for reducing the relative stem growth of graminaceous crops, said compounds are dissolved or dispersed in 50/50 aqueous/acetone mixtures and applied to the foliage of seedling barley plants (Larker variety) growing in individual cups approximately 7.5 cm square. A sufficient amount of a spreader-sticker is added to the mixture to provide approximately 0.1% by weight thereof in the mixture. The principal functioning agents of the spreader-sticker used are: alkylarylpolyethoxy ethanol, free and combined fatty acids, glycol ethers (di-alkyl), benzenedicarboxylate and isopropanol. This spreader-sticker has a specific gravity of 0.90 at 20/20° C.; a density of 898.5 g/L at 20° C.; a surface tension of 30 dynes/cm at 0.1% concentration in water; and a pH of 6± 0.5 as a liquid spray film. It is marketed as BioFilm® by Colloidal Products Corporation of Sausolito, Calif.

The treatment consists of spraying the compound in acetone:water (1:1) at the rate of 747 liters per hectare on seedling barley plants, using a moving nozzle which travels along a stationary track above the plants, at a constant speed. In these tests, compound is applied at rates of from 0.056 to 6.72 kg per hectare.

The treated plants are placed on greenhouse benches and watered and fertilized in accordance with normal greenhouse procedures.

Three weeks after treatment, plants are measured, and in some instances harvested and weighed. The height of control plants and treated plants are recorded and reported in Table I below.

                                      TABLE I                                      __________________________________________________________________________     Evaluation of Test Compounds for Reducing the Relative Stem Growth             of Barley Plants (Larker Variety); Said Compound having the Structure:          ##STR8##                                                                                                       Barley                                                                  Rate   Height                                                                              Weight                                   R.sub.1                                                                             R.sub.2                                                                               R.sub.3                                                                             R.sub.4  kg/Hectare                                                                            cm   gram                                     __________________________________________________________________________     Control                   --     11.7 16.2                                     CH.sub.3                                                                            CH(CH.sub.3).sub.2                                                                    CH.sub.3                                                                            CH.sub.3 0.56    9.5 14.4                                                                0.165  9.8 15.0                                                                0.056 10.8 14.2                                     Control                   --     17.8 15.3                                     (CH.sub.2).sub.5                                                                           H    CH.sub.3 6.72   16.3 16.0                                                               3.36   17.8 17.2                                                               1.12   16.8 15.4                                     Control                   --     33.3 --                                       (CH.sub.2).sub.5                                                                           CH.sub.3                                                                            CH.sub.3 2.24   32.0 --                                                                 0.56   32.2 --                                                                 0.11   33.6 --                                       CH.sub.3                                                                            CH(CH.sub.3).sub.2                                                                    H    CH.sub.2CCH                                                                             2.24   Dead --                                                                 0.56   21.8 --                                                                 0.11   33.2 --                                       __________________________________________________________________________

EXAMPLE 4 Evaluation of Imidazolinyl Benzamides for Reducing the Stem Growth of Corn and Snapbeans

These evaluations are made following the procedure of Example 3, but substituting corn and snapbeans for barley. In these tests, seedling corn and snapbean plants are sprayed with aqueous/acetone (1:1) mixtures having a sufficient amount of test compound dissolved or dispersed therein to provide from 0.056 to 6.72 kg/hectare of test compound per treatment.

The varieties of corn and snapbeans used in these tests are, respectively, Field Corn FR-619 and Greensleeves.

Reduction of stem growth of treated plants is evident from the data obtained in these tests and reported in Table II below.

                                      TABLE II                                     __________________________________________________________________________     Evaluation of Test Compounds for Reducing the Relative Stem Growth             of Corn and Snapbeans; Said Compound having the Structure:                      ##STR9##                                                                                            Corn    Snapbeans                                                        Rate  Height                                                                             Weight                                                                             Height                                                                             Weight                                       R.sub.1                                                                           R.sub.2                                                                               R.sub.3                                                                           R.sub.4                                                                           kg/Hectare                                                                           cm  gram                                                                               cm  gram                                         __________________________________________________________________________     Control         --    86.0                                                                               25.3                                                                               42.5                                                                               27.0                                         CH.sub.3                                                                          CH(CH.sub.3).sub.2                                                                    H  CH.sub.3                                                                          2.24  81.0                                                                               25.4                                                                               37.0                                                                               24.4                                                         0.44  84.6                                                                               22.3                                                                               41.8                                                                               24.0                                                         0.11  76.8                                                                               19.8                                                                               41.0                                                                               22.8                                         CH.sub.3                                                                          CH(CH.sub.3).sub.2                                                                    CH.sub.3                                                                          CH.sub.3                                                                          0.56  70.2                                                                               19.8                                                                               23.0                                                                               16.2                                                         0.165 80.2                                                                               21.5                                                                               30.6                                                                               20.6                                                         0.056 77.8                                                                               23.2                                                                               37.8                                                                               20.2                                         Control         --     78.9                                                                              23.8                                                                               36.2                                                                               22.4                                         CH.sub.3                                                                          CH(CH.sub.3).sub.2                                                                    CH.sub.3                                                                          CH.sub.3                                                                          0.56  62.8                                                                               16.7                                                                               21.6                                                                                9.3                                                         0.165 61.0                                                                               12.8                                                                               20.0                                                                               18.3                                                         0.056 73.0                                                                               16.8                                                                               20.6                                                                               18.3                                         Control         --    77.9                                                                               33.4                                                                               35.6                                                                               21.4                                         (CH.sub.2).sub.5                                                                         H  CH.sub.3                                                                          6.72  76.0                                                                               38.6                                                                               30.6                                                                               20.8                                                         3.36  73.4                                                                               35.6                                                                               35.4                                                                               22.5                                                         1.12  70.8                                                                               33.0                                                                               37.4                                                                               21.8                                         __________________________________________________________________________

EXAMPLE 5 Evaluation of Imidazolinyl Benzamides as Plant Growth Regulating Agents for Bean-Producing Legumes

In these tests, seedling soybean plants, 21 days old, are sprayed with solutions or dispersions of test compound in 50/50 aqueous/acetone mixtures. Test solutions or dispersions contain sufficient amounts of test compound to provide 0.033 or 0.11 kg/hectare thereof to the plant foliage when the plants are sprayed, as described in Example 1 above.

Test solutions, likewise, contain 0.1% by weight of a spreader-sticker, such as described in Example 3 above.

After spraying, the plants are placed on greenhouse benches and watered and fertilized in accordance with normal greenhouse procedures.

Two months after treatment, the plants are transplanted to individual 18 cm pots and returned to the greenhouse for further development.

Twelve weeks after spraying, the test is terminated. The plants are examined, harvested, weighed, the number and weight of the pods on each plant determined, and the pods dried and weighed again.

In these tests, two varieties of soybeans, Bragg and Fiskeby V, were used. Five plants per treatment were employed and the results, as regards plant height, pod production and pod weight, averaged. The data obtained are reported in Table III below.

                                      TABLE III                                    __________________________________________________________________________     Evaluation of Imidazolinyl Benzamides for Reducing Relative Stem Growth        of Soybeans and Increasing Bean Yield                                                        Soybean Varieties                                                              Fiskeby V      Bragg                                                                     Average        Average                                                                             Average                                                    Fresh                                                                               Average   Fresh                                                                               Dry                                                   Average                                                                             Weight                                                                              Fresh                                                                               Average                                                                             Weight                                                                              Weight                                           Average                                                                             Number                                                                              Beans                                                                               Weight                                                                              Number                                                                              of Pods                                                                             of Pods                                          Plant                                                                               Beans                                                                               per  per  of Pods                                                                             per  per                                        Rate  Height                                                                              per  Plant                                                                               Plant                                                                               per  Plant                                                                               Plant                              Compound                                                                               kg/Hectare                                                                           cm   Plant                                                                               grams                                                                               grams                                                                               Plant                                                                               grams                                                                               grams                              __________________________________________________________________________     Control --    43.2 32.8 34.9 --   --   --   --                                 o-(5-Isopropyl-                                                                        0.112 39.4 29.6 34.2                                                   5-methyl-4-oxo-                                                                        0.033 38.0 34.2 34.3                                                   2-imidazolin-                                                                  2-yl)benzamide                                                                 Control --    --   --   --   340.9                                                                               5.0  0.50 0.08                               o-(5-Isopropyl-                                                                        0.112                278.4                                                                               11.2 1.22 0.23                               5-methyl-4-oxo-                                                                        0.033                304.5                                                                               5.2  0.48 0.10                               2-imidazolin-                                                                  2-yl)benzamide                                                                 __________________________________________________________________________

EXAMPLE 6 Evaluation of Imidazolinyl Benzamides as Tobacco Sucker Control Agents

To determine the effectiveness of test compounds for inhibiting bud growth on tobacco plants, Xanthia tobacco plants growing in 18 cm individual pots are topped. Three days after topping, when buds have developed to 1 to 1.5 cm in length, the topped plants are sprayed with an aqueous/acetone (1:1) solution or dispersion of test compound. The solution or dispersion contains 0.1% by weight of a spreader-sticker, such as described in Example 3, and 20 or 100 mg of test compound in 1000 ml of solution. Each plant is sprayed with 200 ml of solution containing 4 or 20 mg of test compound. Five plants per treatment are employed. After spraying, the plants are placed on greenhouse benches and cared for in accordance with normal greenhouse procedures. Three weeks after treatment, all plants are examined and observations recorded. Untreated plants and plants treated with maleic hydrazide (commercial tobacco desuckering agent) are used as controls.

Data obtained are reported in Table IV below, where it can be seen that 20 mg per plant of test compound provides 78.9% bud inhibition; whereas, the commercial bud inhibitor provides only 64.0% bud inhibition.

                  TABLE IV                                                         ______________________________________                                         Tobacco Bud Inhibition                                                                                  Average   %                                                                    Bud       Inhibition                                                 Rate      Growth    Tobacco                                     Compound       mg/Plant  cm        Buds                                        ______________________________________                                         Untreated Control                                                                             --        28.9      --                                          Maleic Hydrazide                                                                              2         28.9      0                                                          4         25.0      13.5                                                       20        10.4      64.0                                        o-(5-Isopropyl-                                                                               4         28.1       2.8                                        5-methyl-4-oxo-                                                                               20         6.1      78.9                                        2-imidazolin-2-yl)-                                                            N,N-dimethylbenzamide                                                          ______________________________________                                     

I claim:
 1. A method for reducing the relative stem growth of plants comprising: applying to said plants a plant growth regulating amount of a compound having the formula: ##STR10## wherein R₁ is alkyl C₁ -C₄ ; R₂ is alkyl C₁ -C₆, cycloalkyl C₃ -C₆, alkenyl C₂ -C₄, phenyl, halophenyl or benzyl; and when R₁ and R₂ are taken together with the carbon to which they are attached they may form cycloalkyl C₃ -C₆ optionally substituted with methyl; R₃ and R₄ each individually represent hydrogen, alkyl C₁ -C₄, alkenyl C₃ -C₅, alkynyl C₃ -C₅, or benzyl; and when R₁ and R₂ represent different substituents, the optical isomers thereof.
 2. A method according to claim 1, wherein the plants are crop plants selected from the group consisting of graminaceous crops, and bean-producing legumes.
 3. A method according to claim 1, wherein the compound is o-(5-isopropyl-5-methyl-4-oxo-2-imidazolin-2-yl)benzaminde.
 4. A method according to claim 1, wherein the compound is N,N-dimethyl-o-(5-isopropyl-5-methyl-4-oxo-2-imidazolin-2-yl)benzamide.
 5. A method according to claim 1, wherein the compound is N-methyl-o-(5-isopropyl-5-methyl-4-oxo-2-imidazolin-2-yl)benzamide.
 6. A method according to claim 1, wherein the compound is N-methyl-o-(4-oxo-1,3-diazaspiro[4,5]dec-2-en-2-yl)benzamide.
 7. A method according to claim 1, wherein the compound is o-(4-oxo-1,3-diazaspiro[4,5]dec-2-en-2-yl)benzamide.
 8. A method according to claim 1, wherein the compound is N,N-dimethyl-o-(4-oxo-1,3-diazaspiro[4,5]dec-2-en-2-yl)benzamide.
 9. A method for reducing the relative stem growth of graminaceous crops and bean-producing legumes by applying to said plants about 0.03 to 3.36 kg per hectare of a compound having the formula: ##STR11## wherein R₁ is alkyl C₁ -20 C₄ ; R₂ is alkyl C_(1-C) ₆, cycloalkyl C₃ -C₆, alkenyl C₂ -C₄, phenyl, halophenyl or benzyl; and when R₁ and R₂ are taken together with the carbon to which they are attached they may form cycloalkyl C₃ -C₆ optionally substituted with methyl; R₃ and R₄ each individually represent hydrogen, alkyl C₁ -C₄, alkenyl C₃ -C₅, alkynyl C₃ -C₅, or benzyl; and when R₁ and R₂ represent different substituents, the optical isomers thereof.
 10. A method according to claim 9, wherein the compound has the formula of claim 9, but R₁ is methyl; R₂ is alkyl C₁ -C₃, cyclohexyl or when R₁ and R₂ are taken together with the carbon to which they are attached they may represent cyclohexyl; R₃ and R₄ each individually represent hydrogen or alkyl C₁ -C₃ ; and when R₁ and R₂ are different, the optical isomers thereof. 